Catheters, a term which also covers endoscopes in this document, are being increasingly used for intravascular or intercardial treatment, with applications in the gastro-intestinal tract also being possible. To this end the catheter is introduced into the elongated hollow organ, and, following the shape of the organ, it has to negotiate multiple curves in the vessel or the intestine. Following the curves is made easier by making the catheter relatively flexible. This flexibility however makes it more difficult to push the catheter forward manually since such a catheter is as a rule advanced by the doctor from outside the patient. With multiple curves the pushing force is used up in adapting the shape of the catheter, which means that where there are curves in the organ, the catheter bends ever more and de facto it no longer moves forward. Simultaneously, the deformation of the catheter has the effect of expanding the walls of the organ which causes pain and also brings the danger of injury. To achieve any advance at all, particularly for any catheter that is inserted a relatively long way into an organ, essentially far more force has to be expended to move it forward and applied than would actually be necessary if the catheter were able to follow the forward movement force without “losses”.